Size Perceptions Under Several Field Conditions

The apparent increase in the size of the moon compared with its size at zenith has been of interest for centuries. Unlike previous research, this study was not conducted in the natural setting, but instead employed the laboratory. This permitted study of theoretical variables in isolation and combination. Variables studied were eye elevation, photic gradients, terrain characteristics, apparent distance and movement. Results show that natural conditions were simulated satisfactorily. It is concluded that present uni‐factor theories are not sufficient for explanation of the phenomenon. All factors yield illusory effects in isolation. Results suggest that factors are not all additive regarding their size effects.